The present invention relates to a tape cassette for use in audio and video tape recorders, data recorders and so forth and, more particularly, to a tape cassette having a swingable cover usually covering and protecting the tape stretched at the front side of the tape cassette and being adapted to swing to expose the tape as necessitated, and as well as a cover lock which normally locks the cover against swinging.
Referring to FIG. 1 showing an essential part of a VHS type tape cassette, a conventional tape cassette 1 for use in, for example, a video tape recorder (VTR) has a cover 3 which is swingable around a shaft 3a so as to selectively cover and protect a tape 2 (shown by two-dot-and-dash line) stretched along the front side of the tape cassette 1. As will be seen from FIG. 2 which is an exploded perspective view, the swingable cover 3 is prevented from swinging by a lock member 4. When the tape cassette 1 is inserted into the cassette holder (not shown) of the VTR, a releasing member (not shown) attached to the cassette holder pushes a projection 5 on the locking member 4 in the direction of an arrow 6, so that the engagement between a recess provided in the cover 3 and a claw 7 provided on the locking member 4 as shown in FIG. 3 no longer exists (they are disengaged) as shown in FIG. 4, thereby permitting rotation of the cover 3 in the direction of the arrow 8 shown in FIG. 1.
The operation of the cover locking member 4 will be further explained with reference to FIG. 2 in which only the lower half part of the tape cassette 1 is shown to facilitate the understanding of the invention. The locking member 4 has a shaft 11 rotatably held by recesses 10 in the lower half part 9, and is biased by a spring 12 in the direction of the arrow 13 so as to make contact with the inner side of the wall 14 of the lower half part 9. The projection 5 of the locking member 4 and the locking claw 7 extend through holes 15 and 16 formed in the wall 14. As the releasing member (not shown) is moved in the direction of the arrow 6, the projection 5 is pushed so that the locking member 4 is rotated by a distance L in the direction of the arrow 17 as indicated by an arrow 17, thereby disengaging the cover 3 and the locking claw 7 as explained above in connection with FIGS. 3 and 4.
In the conventional cover locking means having the described construction, the unlocking motion takes place in the longitudinal direction of the tape cassette, so that the length constituting the locking means is increased as schematically shown in FIG. 5. This arrangement, therefore, is not suitable for use in a small tape cassette, although it can effectively be used for a comparatively large tape cassette. Namely, when this arrangement is applied to small-sized tape cassette, the length k of the opening for receiving a post (not shown) during extraction of the tape 2 is made small to make it difficult to extract the tape 2.
As typical examples of the tape cassette having a swingable cover, tape cassettes of the VHS system and the .beta. system will be explained hereinunder, with reference to FIGS. 6 and 7, respectively. After mounting the tape cassette 18, 19 in a cassette holder 20, 21, the tape cassette 18, 19 is lowered together with the cassette holder 20, 21 in the direction opposite to the arrow 22, 23 to thereby load the tape cassette on the machine. In order to facilitate the understanding, the cassette holder 20, 21 in each of FIGS. 6 and 7 is shown in a schematic perspective view with its top panel removed. In order to prevent any insertion of the tape cassette 18, 19 fully into the loading position on the video tape recorders or the like in an erroneous orientation or posture such as upside down posture, the tape cassette 18, 19 is provided with asymmetrical grooves generally referred to as mis-insertion preventing grooves. More specifically, in the tape cassette 18 of the VHS system shown in FIG. 6, a notch 28 is formed substantially in the center of lower end of the swingable cover 27 which covers the tape (shown by one-dot-and-chain line) 26 stretched along the front surface of the tape cassette 18. In addition, mis-insertion preventing grooves (not shown) are provided in the bottom surface of the tape cassette 18 at positions corresponding to the notch 28. On the other hand, the cassette holder 20 is provided with protrusions 29 at its portions corresponding to these notch and grooves so that the tape cassette 18 can be fully received by the cassette holder 20 only when the tape cassette 18 is inserted in the correct posture. In this case, when there is slack in the tape 26 it causes an offset of the tape position from the correct position in the breadthwise and the tape 26 may be caught and damaged by the protrusion 29 accidentally. In addition, the notch 28 formed in the cover may undesirably permit foreign matter to come into the tape cassette even when the cover 27 is in position to completely cover the tape 26, so that the perfect protection of the tape may not be attained. Referring now to the tape cassette 19 of the .beta. system, this tape cassette 19 is provided with mis-insertion preventing grooves 30, 31 formed in both side walls thereof at heights h.sub.1 and h.sub.2 as measured from the bottom thereof. The cassette holder 21 is provided with projections 32, 33 at portions thereof corresponding to the grooves 30, 31, so that the tape cassette 19 can be received by the cassette holder 21 only when the projections 32, 33 are aligned with associated grooves 30, 31, i.e. only when the tape cassette 19 is oriented correctly with respect to the cassette holder 21. In this case, since mis-insertion preventing grooves 30, 31 are formed in both side walls of the tape cassette 19, the breadth of the tape cassette is increased correspondingly, which goes quite contrary to the demand for a reduction in size of the tape cassette. The tape cassette and cassette holder shown in each of FIGS. 6 and 7 employs the following arrangement in order to correctly position the tape cassette 18, 19 within the cassette holder 20, 21 in the direction of insertion, thereby to ensure the correct loading of the tape cassette in the video tape recorder or the like. Namely, in the tape cassette the VHS system shown in FIG. 6, contact portions 36, 37 are formed on the portions of the front surface thereof corresponding to protrusions 34, 35 on the cassette holder 20. On the other hand, the tape cassette 19 of the .beta. system shown in FIG. 7 has contact portions 40, 41 formed in the portions of the front surface thereof corresponding to the protrusions 38, 39 provided on the cassette holder 21. In order to prohibit the opening of the swingable cover 27 when the tape cassette 18, 19 is not used, each tape cassette is provided with a cover lock (not shown). More specifically, in the tape cassette of the VHS system shown in FIG. 6, the locking is effected by mutual engagement between the cover locking member (see FIG. 2) and a projection 5, as explained before. For unlocking the cover, an unlocking member (not shown) provided on the cassette holder 20 presses the projection 5 when the insertion of the tape cassette 18 in the direction of the arrow 24 is completed. In the .beta. system shown in FIG. 7, the following unlocking arrangement is employed. As notch 43 is formed in the swingable cover 42 so as to cover the tape 47 (shown by one-dot-and-dash-line) stretched along the front side of the tape cassette 19. A groove (not shown) is provided in the bottom side of the tape cassette 19 in the position corresponding to the notch 43. An unlocking portion (not shown) facing the above-mentioned groove is moved by a protrusion 44 on the cassette holder 21 which comes into the notch 43 as the tape cassette 19 is inserted in the direction of the arrow 25, so that the cover is unlocked.
In each of the arrangements shown in FIGS. 6 and 7, there is provided a cover opening member 45, 46 which is adapted to be raised in the direction of the arrow 22, 23 to lift the lower end of the cover 27, 42 to thereby open the latter, as the cassette holder 20, 21 together with the tape cassette 18, 19 is moved downward into the video tape recorder or the like. Grooves (not shown) are formed in the tape cassette 18, 19 to present a passage for the cover opening member coming into the tape cassette 18, 19.
In the conventional arrangements shown in FIGS. 6 and 7, it is necessary to dispose on the front side of the tape cassette 18, 19 all of the members or parts such as the mis-insertion preventing grooves 30, 31 (omitted from FIG. 6), contact portions 36, 37, 40, 41 for correctly positioning the tape cassette 18, 19 in the cassette holders 20, 21, projection 5 (omitted from FIG. 7) for unlocking the swingable cover 27, 42, and the grooves (not shown) presenting the passageways for the cover opening member 45, 46 for opening the cover 27, 42.
In consequence, large lengths are required for accomodating these members or parts, as indicated at l.sub.1 and l.sub.2, l.sub.3 in FIGS. 6 and 7, respectively. Such large lengths could be obtained when the tape cassette has a comparatively large size but can hardly be obtained when the tape cassette has a small size. Thus, the conventional arrangements shown in FIGS. 6 and 7 are quite unsuited for small-sized tape cassette intended for use in a compact instrument such as a video tape recorder in which the tape stretched on the front side of the instrument is pulled out by an inner post to form a predetermined tape path.